Want to know how to load test a car battery without a fancy tester? Your car
has everything you need right on board to do the test without the use of a
voltmeter or load tester. I have created this guide which will go over an easy
step by step instruction process that will allow you to test your own battery
while saving you money.
Here are the main reasons the unit will fail:
Battery is more than three years old
The alternator is not charging or overcharging the electrical system
There is a electrical (parasitic) draw on the system
To get started please watch the video below and then follow down the guide to
see the additional information we have added on this subject.
If you are on the page because the engine will not start then you will need to do some checking first.
Engine is not starting
If the battery warning light has been on while the engine is running then you
need to test the alternator first because the battery might not be the problem
because it is not getting recharged.
If you have a new battery and it goes dead overnight something in the
electrical system is draining it down.
for an electrical draw
Now then, let's get started.
If the battery warning light is not on or gauge shows it the system it charging or
the charging system checks out okay using a voltmeter let's continue.
A battery can fail in one of two ways, the first way is very quickly in
others word you go out to your car and without warning it will just be dead.
When this happens there isn't much you can do but wait for a tow truck or
someone you know to boost the battery start using jumper cables. In this case a
jump may not even help because the battery is so far gone it just dumps (pulls
in) all the voltage supplied to it.
The second way the battery can go bad is a slow decline of voltage and
amperage which gives you little signs along the way such so slow engine
cranking in this case you will notice the starter sounding a little different.
Once you notice this it's up to you to be preventive and change the battery before total failure occurs. The best way to confirm this is with the
When working with a battery
wear protective eye wear and gloves, stand
clear of the battery while the engine is being cranked over. Open the hood to locate
the battery and check it's condition, you are looking for leakage and bulging
which indicating warped internal plates that can short circuit and also
corrosion which can eat the positive and negative cable away which will cause
additional problems, these are all signs of problems.
Now, turn the headlights on and leave them on for about 15 minutes.
After waiting and while the headlights are still on, try
cranking the engine over while watching the headlight bulb brightness.
The bulbs should only dim slightly when using
the starter, if they dim way down and go out or you notice the engine
is cranked over slowly followed by a machine
gun style of clicking noise, the battery can not supply the voltage needed to operate and must be replaced.
If the unit was good it should be able to withstand this load test.
The electrical cables that supply power and ground can inhibit electrical flow, look for bulges near the top of the cable
ends near the terminals. These bulges indicate corrosion expansion caused by the
chemical reaction between the acid and copper wire inside the cable and should be replaced.
A non deep cycle battery must have a rest period or downtime to allow the plates inside
time to cool. A battery subjected to constant charge and complete discharge will
fail prematurely unless it is a deep cycle type unit. All batteries are a hazardous material
and must be disposed of at a local parts store or recycle center.
If you have any questions about the information or testing, please visit our
forum where thousands of answers have been given by our online mechanics. Learn